In the past in mobile phones, etc., if a destination user terminal does not respond to a phone call transmitted from a source user terminal, the source user terminal is connected with the voice mail system to store a voice message in the voice mail system.
Such a voice mail system is known to transmit a notification that a voice message is stored in a voice mail system when a voice message is stored.
For example, Patent Document 1 discloses the constitution in which the text message saying that a voice message is stored in a voice mail system 1 is transmitted to a user terminal so that the user can listen to the voice message by connecting to the voice mail system 1.